1. Field of the Invention
The invention relates to a device for reading flexible storage foils.
2. Background Art
Recently, flexible storage foils are being used instead of X-ray films. When ionizing radiation or X-rays impinge on such foils, metastable storage centers will be produced, which are lattice defects or color centers (or generally trap centers), which have trapped a charge carrier (electron or hole) produced by the ionizing radiation. Such storage centers are stable over long times. If the storage centers are illuminated with a very narrow laser beam of corresponding wave length, the storage centers will be moved into a higher excited state, from which the charge carriers can recombine under emission of light called photo-stimulated luminescence (PSL). The latter process is also shortly referred to as recombination of storage centers.
At such points of the storage foil, whereon a larger amount of X-rays has impinged, one obtains by reading this point using a reading light beam, a higher amount of light quanta than at such points, which have received only a few X-rays. If the storage foil is scanned in two dimensions, the output signals of a light detector receiving the PSL corresponds to the optical density of a conventional X-film.
In known reading devices, two dimensional scanning of the storage foil is obtained by arranging the storage foil on the outer surface of a drum, by rotating the drum and by moving a reading unit along a generating line of the drum. The reading unit includes a laser source and a light detector.
Such drum type scanners, which are also known for scanning images, are disadvantageous in that they have larger moving masses and in that the scanning velocity which can be achieved is only small due to this fact so that the scanning process takes a long time. It is thus an object of the present invention provide a reading device, wherein the moving masses are smaller and which allows high scanning velocities and short scanning times.
In a reading device in accordance with the present invention the storage foil support has the form of a part cylinder or of a cylinder, and a light deflecting element is arranged on the axis of this cylinder's surface. This deflecting element produces a fine rotating reading light beam, which scans the interior surface of the storage foil. This light deflecting element requires only very small dimensions and is of small mass, only. Due to this construction, the reading device in accordance with the present invention can work well with higher speed or rpm.
These and other objects of the present invention will become apparent in light of the present specification, claims and drawings.